In a manufacturing process of a semiconductor substrate, such as at an annealing step, the semiconductor substrate is treated with heat in a vacuum chamber. In such a process, uniformly heating the semiconductor substrate to reduce the temperature distribution has a great influence on the yield; therefore, more precise temperature control is desired.
In the heat treatment of the semiconductor substrate, a shaft-equipped heater for supporting and heating the semiconductor substrate is used. The shaft-equipped heater is composed of a sheath heater-embedded heater plate on which the semiconductor substrate which is an object to be heated is placed and a shaft for supporting the heater plate. The shaft-equipped heater having this configuration has a problem that there is a decrease in temperature of a plate central part because a shaft central part is less subject to heat input due to a constraint on routing of a sheath heater wire, and also heat dissipation via the shaft is likely to occur.
Meanwhile, there has been proposed a technology to improve the temperature distribution of a heater plate in such a manner that the heater plate constituted of metal or metal alloy having high thermal conductivity and a shaft constituted of metal or metal alloy having lower thermal conductivity than material of the heater plate are joined by brazing or the like, thereby suppressing the heat conduction to the shaft.
Furthermore, there has been proposed a ceramic heater whose heater plate is a ceramic sintered body, wherein a shaft part formed of material having lower thermal conductivity than a heater plate part and the heater plate part are joined (see Patent Literature 1).